1. Field of the Invention
The present invention relates to a coil inspection technology for a magnetic resonance imaging (MRI) apparatus that can change a combination of coil elements for receiving a magnetic resonance (MR) signal and assign the combination of the coil elements to a channel.
2. Description of the Related Art
A magnetic resonance imaging performed by an MRI apparatus is an imaging method in which a nuclear spin of a patient placed within a static magnetic field is magnetically excited by a radio-frequency signal of a Larmor frequency, and an image is reconstructed from an MR signal generated in connection with the excitation.
In order to perform this imaging method, the MRI apparatus includes a static magnetic field magnet that generates the static magnetic field, and a mechanism that applies a gradient magnetic field pulse and a radio-frequency magnetic field pulse to the patient according to a predetermined pulse sequence. Among the pulses, the gradient magnetic field pulse is transmitted to the patient through a gradient magnetic field coil. The gradient magnetic field coil is disposed within a bore in the static magnetic field magnet and is connected to a gradient magnetic-field power source. Similarly, the radio-frequency magnetic-field pulse is transmitted to the patient through a radio-frequency coil for transmission. The radio-frequency coil for transmission is disposed within the bore in the static magnetic field magnet and is connected to a transmitter. On the other hand, a radio-frequency coil for reception is disposed near the patient to receive an MR signal that is composed of a radio-frequency signal and generated from the patient. The radio-frequency coil for transmission and the radio-frequency coil for reception can be combined into a single coil. However, in many instances, dedicated radio-frequency receiving coils for different diagnostic regions are used.
In other words, to acquire an image with high-sensitivity, the patient is imaged with a plurality of surface coils (array coils) as the radio-frequency receiving coils disposed in a region-of-interest of the patient. For example, an array coil consisting of quadrature detection (QD) surface coils arrayed in a body axis direction, such as that described in JP-A H5-261081 (KOKAI), is proposed as a spinal coil. The QD surface coil is a coil formed by disposing a loop-shaped surface coil and a figure-eight shaped surface coil in a superimposed manner. A signal-to-noise (S/N) ratio of the QD coil can be improved as compared to when the figure-eight shaped surface coil is not superimposed.
On the other hand, as described in JP-A 2003-334177 (KOKAI), when an overall abdominal area is imaged, ordinarily, a plurality of surface coils is disposed such as to surround the patient and receive a signal emitted from the overall abdominal area. As the surface coils, array coils consisting of a plurality of loop coils arrayed along a body surface are often used.
In recent years, an MRI apparatus has been developed that can change a combination of a plurality of coil elements and assign the coil element combination to a channel (refer to, for example, JP-R 2006-141444 (KOKAI). In this MRI apparatus, sensitivity distribution can be optimized for each region to be imaged as a result of the combination of coil elements being changed and the coil element combination being assigned to a channel.
However, in the MRI apparatus that can change the combination of coil elements and assign the coil element combination to a channel, an inspection of the radio-frequency receiving coils during installation and the like requires time and effort.
Namely, in order to inspect all coil elements and portions used when the coil elements are combined, imagings are required for each coil element combination, and the inspections are required for using collected pieces of data and images. Therefore, when a large number of coil elements are present, the inspection is required for several tens of thousands of combinations, thereby requiring a large amount of time.